This application is based on and incorporates herein by reference Japanese Patent Application No. 2001-397355 filed on Dec. 27, 2001.
1. Field of the Invention
The present invention relates to a motor that includes a coupling means for coupling between a rotatable shaft of a motor main body and a worm shaft of a speed reducing unit.
2. Description of Related Art
A motor is used as a drive source for a power window system installed in a vehicle door. Such a motor includes a motor main body and a speed reducing unit, which are drivingly coupled together. The motor main body rotates a rotatable shaft. The speed reducing unit receives a speed reducing mechanism that reduces rotational speed of the rotatable shaft. The motor for the power window system needs to have an arrangement, which restrains rotation of an output shaft of the motor when rotational force is applied to the output shaft due to a downward load exerted to a window glass, for example, by a weight of the window glass of the parked-vehicle or by vibrations of the running vehicle.
To address the above disadvantage, various motors for the power window system have been proposed. One such motor includes a clutch that is interposed between the rotatable shaft of the motor main body and the worm shaft of the speed reducing mechanism. The clutch transmits rotational force of the rotatable shaft, which is rotated upon operation of the motor main body, to the worm shaft to transmit the rotational force to an output shaft of the motor. However, when rotational force is applied to the output shaft from the load side, the clutch restrains rotation of the output shaft of the motor by restraining rotation of the worm shaft.
Lubricant, such as grease, is applied to predetermined portions of the clutch to restrain wearing of the components of the clutch. The clutch includes rotatable components that rotate integrally with the rotatable shaft. The grease can be moved out of the clutch by centrifugal force of the rotatable components such that the amount of the grease in the clutch becomes insufficient. When the amount of the grease in the clutch becomes insufficient, the rotatable components in the clutch cannot be smoothly rotated, disturbing rotation of the motor.
The present invention addresses the above disadvantage, and it is an objective of the present invention to provide a motor, which includes a coupling means for coupling between a rotatable shaft of a motor main body and a worm shaft of a speed reducing unit and is capable of restraining effluence of lubricant used in the coupling means.
To achieve the objective of the present invention, there is provided a motor including a motor main body, which includes a rotatable shaft, a speed reducing unit, which is connected to the motor main body and includes a worm shaft, a coupling means for coupling between the rotatable shaft and the worm shaft, and a stopper, which restrains axial movement of at least part of the coupling means. The rotatable shaft is rotated upon energization of the motor main body. The worm shaft is rotatably supported and is substantially coaxial with the rotatable shaft. The coupling means retains lubricant. The speed reducing unit further includes at least one surrounding wall arranged radially outward of the coupling means. Each of the at least one surrounding wall has a single axial length and an end surface arranged on a motor main body side of the at least one surrounding wall, and the end surface of each of the at least one surrounding wall is engaged with the stopper. The coupling means is substantially entirely surrounded by at least one of the stopper and the at least one surrounding wall in an imaginary plane, which is substantially perpendicular to the axis of the worm shaft, to substantially restrain radially outward effluence of the lubricant.